The general aim of this research is to study the fine structure and cytochemistry of invertebrate neural tissues, especially synapses, during the course of degeneration and regeneration in the central nervous system. Specifically, following ablation of an antennule or an eyestalk in a decapod crustacean, light microscopic, ultra-structural, and cytochemical (cholinesterase, acid phosphatase, monoamines) studies will be made of representative regions along the stumps of the periphera antennular nerve of the optic peduncle, in the relevant fiber tracts within the brain, and in the appropriate synaptic neuropil areas of brain. Following antennule removal, the existence, time course and characteristics of degenerative and regenerative phenomena will be observed during the course of neural reorganization which must occur during development of a new antennule and formation of functional synapses by new antennular sensory neurons as their axons grow into the brain from their origin point in the periphery. The morphological and cytochemical features of this normally regenerating sensory system will be compared with those occurring in a system where duplicate regeneration does not occur and permanent degenerative phenomena are known (grossly) to take place--namely in the optic and associated integrative systems following removal of an entire eyestalk.